In conventional editing of moving images, moving images are concatenated. Since the data size of moving image data is normally large in digital signal processing, moving image data is often encoded (compressed) before use. Examples of general encoding methods for image data include Moving Picture Experts Group (MPEG), Advanced Video Coding (AVC), and High Efficiency Video Coding (HEVC).
In a case where moving images are concatenated in the above described manner using moving image data encoded as above, one bitstream is generated from more than one bitstream. In such bitstream generation, each bitstream may be decoded and decompressed, and the bitstreams be then concatenated. The moving images after the concatenation may be encoded, to generate one bitstream. In that case, the processing load might become larger, as the data size of the bitstreams becomes larger.
In view of this, smart rendering editing has been developed as a technology for shortening the encoding time and preventing image quality degradation when moving image data encoded as above are clipped and edited with frame precision (see Patent Document 1 and Patent Document 2, for example).
Meanwhile, in AVC and HEVC, the concept of a hypothetical reference decoder (HRD) is introduced so as to transmit bitstreams without any breaking. An encoder needs to generate bitstreams in such a manner as not to cause the hypothetical reference decoder to break. This also applies in encoding in the above described smart rendering editing.